Work vehicles such as wheel loaders, backhoes, loader-backhoes, excavators, skid steers, graders, trenchers, tractors, combines, balers, cotton pickers, telehandlers, forklifts, and other material handling or ground engaging vehicles often include members that are coupled together to pivot with respect to one another at pivot joints. These members are most commonly moved by actuators, for example, hydraulic actuators such as hydraulic cylinders.
In a common arrangement, such as the backhoe attachment of a loader-backhoe, or the excavating attachment to an excavator, two elongate rigid members such as boom swing towers, booms, dippers or buckets are coupled together with a pivot pin at a pivot joint. A hydraulic cylinder extends between and is coupled to the two members. The cylinder pivots the two members with respect to one another about the pivot pin by extending and retracting.
Typically, the pin in a pivot joint has a structure for retaining the pin in place. In one arrangement snap rings are fastened to both ends of the pivot pin. The snap ring on one end prevents the pin from moving in one direction and the snap ring on the other end prevents the pin from moving in the other direction. In another arrangement, a shoulder or head is provided on one end of the pin, replacing one snap ring. The dual snap ring and ring-and-shoulder arrangements are acceptable for pivot joints that are not blind—i.e. when an operator can get access to both ends of the pivot pin.
Blind pivot joints, however, require different structures since one has no access to both ends of the pivot pin in its blind hole. In these situations, pivot pins have been provided with a retainer that is welded to and extends away from the pin. This retainer is fixed to the member in which the pin is inserted, typically with a bolt. This fixes the pin in the member by a connection at just one end, preventing pin movement either into or out of the joint. It also holds the pin stationary with respect to the member to which the retainer is fastened, and thus forces the pin to pivot with respect to one of the two members. Disadvantageously, this welded arrangement holds the pin rigidly with respect to the member, and does not let it float within the pivot pin hole.
An alternative arrangement for blind pivot joints includes a pin with a circumferential groove at one end and a retainer that fits into this groove. An advantage to this arrangement is the pin's ability to (1) wobble, float or self-align slightly within the pivot pin hole and (2) to rotate freely about its longitudinal axis.
Recently, however, this free rotation has been identified as a problem in some situations where the pin binds or corrodes in the pivot pin hole that supports it. In these situations it is beneficial to prevent the pin from rotating.
The free rotation could be prevented by welding the pin and retainer together in the prior art manner. This arrangement would, however, prevent the pin from self-aligning with respect to the hole.
What is needed, therefore, is an improved pivot pin assembly for blind holes that permits the pin to float, wobble or self-align slightly in the hole (like the arrangement with the circumferential groove), yet also retains the pin in a blind hole (like the welded arrangement).
It is an object of this invention to provide such a pivot pin assembly.